When it comes to the 2010 midterm elections, the conventional wisdom in Washington seems largely agreed a few central points: the Democrats are going to lose a bunch of House seats, and how many they lose will depend a lot on the economy and Barack Obama’s approval rating. In fact, in virtually any piece you read about 2010, you’ll see a significant caveat: Democrats will suffer less if the economy improves and Barack Obama’s favorability rating rises.

Veteran election analyst Charlie Cook says Democrats better not count on that:

A whopping 48 of those Democrats — eight more than the size of their party’s majority — are from districts that voted for both Bush and McCain. That America is very different from the Democratic base in blue America, and it sees many major issues very differently.

Resurgent Republic’s findings corroborate a growing view that the cumulative impact of Democratic missteps has reached a critical mass, with Obama receiving some damage and with Democrats in Congress and the Democratic Party receiving much more. Critics point to the Troubled Asset Relief Program; the takeovers of banks and auto companies; an economic stimulus package that they see as ineffectual and stuffed with pork; and climate-change and health care reform efforts as all being contributing factors to Democrats’ decline…

What we are seeing is an electorate growing just as disgusted with the Democratic majority as it did with the Republican one in 2006. The mounting ethics problems of House Ways and Means Committee Chairman Charles Rangel, D-N.Y., combined with ongoing allegations about House Defense Appropriations Subcommittee Chairman John Murtha, D-Pa., and others on his panel threaten to make matters still worse for their party.

Sure, November 2010 is a long way off, and the economy may well be substantially better by then. But Democratic lawmakers, who must face the voters two years before Obama does, should remember that the public’s attitudes tend to eventually harden. Think cement.

Charlie Cook mentions 2006. In that election, Democrats composed a slightly greater portion of the electorate than Republicans – but independent voters voted for Democrat candidates by a decisive margin of 57%-39%.

The silver lining for Congressional Democrats is this: their success is not tied to outside forces – like Barack Obama and the economy. If they turn over a new leaf, they have it in their power to win over independents and save their majorities. All it takes is for Nancy Pelosi and Harry Reid to decide to follow a moderate course, marked by respect for those who disagree, and a willingness to compromise, rather than pursue a hard-left agenda. If they go that route, they may yet be able to convince voters that they deserve to continue to lead.

Feel free to insert your own punchline.